1. Field of the Invention
The invention is related to an arrangement for providing a variable throttle cross-section for a fluid flow, a lift control valve with the arrangement, a hydraulic lift installation with the lift control valve as well as a method for operating the lift installation according to the preambles of the independent claims.
2. Prior Art
Various arrangements for providing variable throttle cross-sections for fluid flows conducted there through are available today for hydraulic and pneumatic installations, namely for regulating pressures and/or volumes as well as also for their measurement. In these cases the variation of the throttle cross-section is done either by external regulating intervention by mechanic, hydraulic, pneumatic or electric regulatory actuators, i.e. in case of control valves, or by the pressure, a pressure difference and/or a flow force of the fluid conducted inside the arrangement, like for example in case of pressure limiting valves or non-return valves. The latter arrangements have the advantage that high operation reliability is reached as a result of the relatively simple hydraulic/pneumatic coupling and the independence from auxiliary energy. It is however disadvantageous that these arrangements are typically only usable in one direction of flow. This is a problem for devices in case in which fluid flows with changing flow direction occur, depending on the operation situation, like in case of lift control valves for hydraulic lift installations, this being solved today by using multiple such arrangements and a complex switching thereof. This imposes however a considerable financial and technical effort and additionally leads to not negligible maintenance costs.